Looking for recommendations for a commercial supplier for long (400bp homology arms) for ssDNA and dsDNA to use for a CRISPR HDR project?
We are using IDT for but ssDNA and dsDNA synthesis. For ssDNA you can use their Megamer ssDNA (http://www.idtdna.com/pages/products/genes-and-gene-fragments/megamers-single-stranded-dna-fragments), which has a synthesis limit of 2Kb, and for dsDNA you can use their gBlocks (http://www.idtdna.com/pages/products/genes-and-gene-fragments/gblocks-gene-fragments), which have a synthesis limit of 3Kb.
For larger fragments we are only using dsDNA and are building plasmids. If you are building into plasmids I would suggest using the Double-Cut strategy so that you do not have to linearize your plasmids and to potentially increase integration rates. However, if your fragment is small enough to fit into a Megamer or gBlock I would suggest using that instead since it is easier to synthesis.